text:
What's the speed callout by the PNF on airliners for?
On all Airliners, there is a speed callout by the PNF at some point during take-off, usually at 80 or 100 KIAS.
Whats the reason for those callouts? And why are some at 80 KIAS and some at 100 KIAS?

@Federico -- this is before V1

@UnrecognizedFallingObject right, sorry. but not too far from it (depending on weight) deleting old comment anyway.

This call serves two main purposes. The first is to verify that both airspeed indicators are showing the same speed. Since airspeed = life, it's best to find out that one of them is faulty on the ground rather than in the air.
The second purpose is to distinguish a high-speed rejected takeoff from a low-speed one. Below 80kts (or 100kts or another speed set by the manufacturer and/or airline), a takeoff would be rejected for almost anything out of the ordinary.
But rejecting a takeoff at high speed carries a lot of risk - like brake fires, tyres exploding, directional control difficulty, etc. So above 80 or so knots, a takeoff will only be rejected in the case of major failures. Some modern aircraft even inhibit minor warnings from appearing after 80kts until the aircraft is airborne, because rejecting the takeoff is not worth the risk, so don't saturate the pilots with unnecessary information.
This page goes into some detail about what you would reject a takeoff for at low speed vs high speed. The criteria may vary slightly amongst airlines but the general themes are the same.

There is a third reason. Many airline SOP's use the 80 or 100 call as a crosscheck against pilot incapacitation.  If the Pilot Flying does not respond, the Non-Flying Pilot will assume control and reject the take-off.


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How far are shortened replies to ATC allowed to go?
Pilots often use non-standard-phraseology for readbacks. Some examples:

ATC: DLM, switch to tower, 121.2
P: tower, for DLM

or

ATC: DLM, identified, climb via the RIDA9 departure
P: roger, climb via, DLM

or

DLM, cleared for takeoff runway 17
P: cleared for takeoff, DLM

The last two example are from two videos by Boldmethod, How To Fly An IFR Departure Procedure With A "Climb Via" and How To Fly An Instrument Arrival Procedure (STAR), used by an ExpressJet-pilot.
Especially the two last ones were a bit shocking to me when I heard a professional pilot using them. So I now want to ask, how far is this "ATC-Slang" allowed to go?

The shortest I have heard was double tapping the push-to-talk without any spoken words as an acknowledgement...

Yes, the "double tap" is valid when the response is "OK", like when ATC says "N12345, current information is LIMA". You can't "double tap" any IFR clearances (they must be read back) or things that require a response.

@RonBeyer So this is really valid? How does a double-tap sound on the radio?

Closely related, maybe a dupe?

@NoahKrasser Only in limited use (basically instead of saying "affirmative" to informational calls, especially if you are doing something like short final and the controller calls out a wind shift). The controller hears it as two "clicks" over the radio. Usually though I will just respond with a portion of my tail sign, like "Zero-Five-Charlie" to let them know it was me.

ATC is required to always use standard phraseology, and tapes are randomly reviewed to verify this--and too many violations gets them pulled off for retraining. This makes sense since talking is literally their entire job and it could be with anyone from students to veterans, including people who don't natively speak the language.
Pilots can use whatever wording they want as long as ATC can understand what they're saying, which naturally leads to shortcuts.  It saves time/effort and helps keep the frequency clear for others. In fact, if/how you abbreviate things is a sign to ATC of how experienced you are. If you read back "climb and maintain three thousand five hundred feet", they'll treat you a bit differently than if you say "up to three point five". Listen to a busy airport or approach on LiveATC and you'll pick up the patterns in just a few minutes.
"Perfection is achieved, not when there is nothing more to add, but when there is nothing left to take away." --Antoine de Saint-Exupery

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text:
Is a TCAS capable of handling three (or more) planes on "crash course"?
I asked myself if the TCAS is capable to handle, the very unlikely situation, that three (or more) planes are simultaneously on "crash course" (Sorry, got no other word for it).
If not, how would the TCAS "react"?
Thanks.

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Why is carb icing an issue in aircraft when it is not an issue in a land vehicle?
As far as I know, the mechanics and physics of an aircraft carburetor are the same as those of an automobile carb. (If I'm wrong, there is no basis for this question.) Aircraft carbs are provided with a carb heat option, while no auto carb that I'm aware of ever came with one.
If carb icing only occurred at the significantly colder temperatures experienced at altitude, I'd understand that this is an aircraft-only issue (or, perhaps, one that might effect only land vehicles at very high latitudes or during extreme cold snaps). However, it is a well established fact that carb icing can occur in temps as high as 20-25°C (68-77°F) even in somewhat low relative humidity (as noted in this answer) - conditions in which automobiles are frequently (commonly, even) operated.
While I certainly appreciate that an engine out event is a significantly more critical issue in an aircraft (quick, where the heck do I land before I crash and die) than it is in a Earth-bound vehicle (signal, check mirrors, coast to a safe stop at the side of the road), why is carb icing even an issue in aircraft when it doesn't seem to be an issue at all in autos?
Note: I realize that few to no automobile engines are carbureted anymore, but that was the norm until nearly the turn of the 21st century.

Wikipedia claims that carb heat was also used on cars and motorcycles, but they don't provide any sources. It might be worth to ask about carb heat on MotorVehicle.SE.

Sounds like this question was asked based on a flawed premise. I should probably close it.

It's a reasonable question @FreeMan, and as I have answered it I have a vested interest in keeping it open ;)

LOL. I'd wondered what happened to your comment. Now I see! OK, I'll leave it. (I have a vested interest in doing so, too!) Of course, closed questions can still get votes, as can answers on closed questions... ;)

Maybe a silly question, but why would ice build up in the carburetor anyway? Unless you enter warm, humid air and the carburetor is still cold and massive enough to cause condensation+icing inside of it.

@Michael see the question/answer I linked for more info on carb icing. Also, there are probably a dozen or more other questions here about it.

I had a Humber Sceptre around 1976 which had (as standard fit) twin Stromberg carbs and a water heating circuit from the engine cooling system. Before that, I had a Ford Cortina Mk 1 which would slow to a crawl going uphill on a motorway on a cold misty morning. If you were quick you could open the hood at Killington Lake services and see the ice still melting off the outside of the carbs.

Your question after lots of introduction was " why is carb icing even an issue in aircraft when it doesn't seem to be an issue at all in autos?". New contributor user67330 described a specific measure undertaken by Mercedes to deal with this problem - whereas many other manufacturers clearly did not do so. Your response to him as a new contributor was puzzingly rude and dismissive.  It is very unclear why you would react to a factual answer, describing a Mercedes solution, in this manner. I suggest an apology is in order.

I don't know in the US but in germany already in the 90s most new cars had one or another type of injection, mainly due to emissions requirements.

@plasmaHH Throttle body fuel injection appeared on American cars around 1980, and carbs were gone by 1990 - couldn't hit the emissions numbers except on very small economy cars (small engine) or larger trucks (reduced smog standard).  This technology march was being forced down the automakers' throats by California, but federal EPA was close on their heels (so abandoning California would be fruitless).  Regardless, even in the late 60s all cars had carb heat - a heat stove on the exhaust manifold, that the air cleaner would draw air from to get target temperature.

Carb icing can occur in car engines, I know of at least two cases where it caused rough running, and that's just my own personal experience. If I remember right VW Beetles are susceptible to this, this is because they are air-cooled, liquid cooled engines on cars typically had a hot water jacket or a hot exhaust element routed nearby to keep the carb warm enough to prevent ice buildup.
The reasons you don't hear about it happening are that 1) liquid cooled engines are less prone, so happens infrequently and 2) with a car you pull over to the side of the road, and in an airplane you make an emergency landing. When you think about the myriad of reliability issues you could have with older car engines you realize that we were simply willing to live with them as they weren't generally life-threatening.

This answer has it, as many airplane engines are air-cooled and many car engines are liquid cooled.  Moreover, cars do not descend at reduced power or glide for extended periods of time, which creates a lot of cooling airflow without adequate engine heat to compensate.  One can only wonder what all that expansion and contraction does to the life of the engine.  Surrounding the carb with warm fluid (oil/antifreeze) and/or burying it in the engine makes a lot of sense.  Turbocharging (which compresses and heats) incoming air is even more appealing, and would do wonders for horsepower.

I wonder, @RobertDiGiovanni, whether if you were in a car at the top of a mountain and basically riding the brake for the majority of the downhill, whether you’d end up icing up a car engine. That situation seems roughly similar to a reduced power/glide situation, or as similar as I can imagine getting in a car without a wholly manufactured scenario

@fyrepenguin try I-40  Flagstaff eastbound.  It's downhill all the way to Texas.

@fyrepenguin Cars built today have coolant lines through the throttle body for heat. Another key difference is that with modern fuel injection, gasoline is vaporized at the valves or directly in the cylinder, where it is much too hot for ice to form. Icing does occur at air filters and charge air coolers (turbo intercoolers), particularly for diesels which use a large amount of air, but it requires much colder ambient temperatures because you don't have the cooling effect of fuel vaporization.

@fyrepenguin or, hopefully, engine braking, using the brakes only to slow for turns.  Modern brakes and fluids are better for sustained descents, seemingly by more than the amount that modern cars are heavier, but there are still distinct advantages to not riding the brakes.  Cars with old air-cooled engines that were apparently more prone to carb icing would have needed care not to overuse the brakes

Ride the brakes all the way down a long descent, @fyrepenguin, and you won't have any brakes left when you really need to stop at the bottom. That's the perfect recipe for boiling the brake fluid! Fluid doesn't compress, allowing you to operate your brakes, but the air (from boiling) does compress, leaving you with no brakes. It's a good way to die. That's why long, steep descents in mountainous areas have truck runoff ramps.

So you are saying you cant pull over in a plane and pop the hood?

@fyrepenguin Riding the brakes would be stupid, use the engine.  I do so reasonably routinely--20 miles that can be done with only a blip of engine power.  I've never done it in icing conditions, though, and it's a fuel injected car.

Yes and for carb icing on land vehicles, should we not be looking at instances like the German army's experience in the extreme Russian winters of WWII? Land vehicles are rarely exposed to the temperatures aircraft face and when they are, their carbs are generally close enough, in small enough compartments to be warmed by their engines. I don't remember whether that last part is also true of aircraft but given the different speeds, I doubt it very much.

GdD is right. In the dying days of carbureted cars, the engine designers came up with a variety of ways to prevent carb icing. One popular method was to use an "oven" (a sheet metal box enclosing a portion of the exhaust manifold through which outside air would be drawn when the engine was cold) that pre-heated the air entering the engine.
My 1973 Subaru had a thermostatically-controlled preheat oven which was broken, but since the car was from California it didn't matter. When I bought it and moved to western Oregon, the first time I drove it through freezing fog it promptly iced up.

The main reason is the same reason carb icing is much less common on Lycoming engines than on Continentals. The carb in Lycomings is bolted directly to the bottom of the oil pan and so the carb body is relatively warm from heat conduction (I've never experienced carb ice in my plane's Lycoming O-290, although I use carb heat religiously anyway, because the potential is always there)
Continental engines have the carb on a spider assembly in front of the oil tank and so it runs colder and has less margin before icing conditions in the throat can be achieved. Piper Cubs with the open cylinders are the worst for this, because there is no cylinder heating of the airflow in the lower cowl to help warm the carb body. They will develop carb ice if you look at them with a mean face on some days.
With cars, the carb is on top, usually bolted right to the engine, so the sweet spot conditions for icing to start are very small, although it can still happen, depending on the carb mounting and the overall amount of heat under the hood. That occasional time when the engine would die mysteriously for no reason, especially after sitting idling for a while, where it starts normally after a few minutes, was probably carb ice, but it would almost certainly take just the right conditions of moderate temperature (60-70F) and very high humidity to overcome all the heat the carb is being bathed in.

Since the answers so far address cars, I'll address motorcycles. A few of the higher end motorbikes of the 1980s-1990s have electrically heated carburetors. For example, the Yamaha VMax has 4 Mikuni BVS34 carburetors, each one having a small threaded cartridge heater powered by 12v. I couldn't find any information on exactly how much power they consume, but they generally thread into the body of the carburetor

and why aren't these electrically heated carburetors present or enough for aviation?

@Federico  A possible reason is that aircraft in the size range of likely interest replace a dumb "good enough" solution with a human-brain driven system which can be optimised  for best results. Considering that multiple factors may be life-impacting, a human brain adds both better potential capability and also a degree of danger.

Aircraft engines are all about reliability, which is often best achieved through simplicity. There is also the matter of approvals for anything fitted to an aircraft. As a result, many technologies common on cars are slow to arrive on aircraft, if ever. Both car and airplane engines solve the carb icing problem in the same way - preheat the air. The difference is that car engines typically have a thermostatic control to automatically regulate the amount of heating, where an airplane engine leaves that task to the pilot. Hence as a pilot you have to be aware of the issue and proper use of the control that mitigates it, but as a motorist you don't even need to know the problem exists.

Curious as to why designers didn't have an electronic trace heating that keeps the carb at a set temperature?

@user13555  Warm air is less dense & so has less oxygen.  It makes combustion less efficient as can be seen by the revs drop when you apply carb heat.  Related:https://mechanics.stackexchange.com/questions/11097/how-does-cold-dry-weather-affect-horsepower

Cars did have carb heat. It was just automatic.
Inside the air cleaner assembly, there was a flapper valve that admitted air either from ram air, or from a heat stove on the exhaust manifold.  There was a bi-metal thermostatic strip that either actuated the flapper door directly, or acted as a pilot valve for a vacuum motor.  It would operate the flapper in an analog manner assuring a minimum temperature for intake air.
GM called this the Thermostatic Air Cleaner system or ThermAC. I have fixed several foul-running cars where the riser pipe or heat stove baffle itself had rotted out.
Obviously this was phased out on newer cars like the Chevy Bolt - seriously though, in the 1980s decade, cars went from 98% carbureted, to 98% fuel injection under computer control (no mechanical backup). Achieving smog standards requires extremely precise fuel control, and nothing less than digital control will do.  That eliminated fine passages prone to icing.  There's nothing delicate in the injector assembly, it blasts fuel at about 2-4 atmospheres of pressure, and it sits very close to the cylinder head.
There is one small passage to a mini-throttle controlled by the computer, called the Idle Air Control valve. That is typically heated by a coolant loop.

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Why is the ICAO prefix for Alaskan airports "P"?
Mainland US airports all (to the best of my knowledge) have ICAO codes beginning with "K", however Alaskan airports all (from a couple of minutes rummaging about on FlightRadar24 and Flight Aware) seem to be prefixed with "P"?
Additional searching seems to indicate that Hawaiian airports are also prefixed with "P".

The airports in Guam, a U.S. territory also start with P. My understanding is that the K designates airports in the contiguous states of the U.S.  U.S. airports in the Pacific take the P designation, those in the Atlantic (Puerto Rico) the T designation. A further delineation is that Alaska airports are PA, Hawaii airports PH, Guam airports PG, Puerto Rico airports PJ.

@Terry TJxx for Puerto Rico.

Sounds like you've got the makings of an answer there, @Terry...

Yeah, close enough to be a dupe, @RalphJ. That's what I get for not doing much searching...

@RalphJ Thanks for catching that. A typo on my part.

Definition from wikipedia:
The ICAO (/ˌaɪˌkeɪˈoʊ/, eye-KAY-oh) airport code or location indicator is a four-letter code designating aerodromes around the world. These codes are defined by the International Civil Aviation Organization, and published in ICAO Document 7910: Location Indicators are used by air traffic control and airline operations such as flight planning.
https://upload.wikimedia.org/wikipedia/commons/thumb/a/ab/ICAO_FirstLetter.svg/1200px-ICAO_FirstLetter.svg.png
This is a map of every ICAO airport code wordwide.
Alaska has PA, PF, PO and PP as airport codes. P = Eastern North Pacific.
PA=USA (Alaska) (also PF, PO and PP)
There is no special meaning behind the letter P and these codes, it's just a classification!!

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Is the clamshell on the AN-72 what causes the Coanda effect?
The AN-72 uses the Coandă effect to improve lift and give it better STOL features.
In this image of an AN-72 (presumably on a takeoff roll) one can see a clam-shell bucket open at the top of the engine.
Source: Wikipedia site listed above
Is this clam shell what kept engine exhaust directed down over the wing to be used for Coandă effect lift enhancement? If not, what are these clam-shell doors for?
One can see in all the other images on that Wiki link that the doors are closed in flight including the first image showing an AN-72 on short final, presumably on a long enough runway that STOL procedures weren't necessary.

This is not a take-off roll for sure. The clamshells are the thrust reversers and the spoilers are extended.

I see that now, @DeepSpace, also noted in the accepted answer.

Those clam-shell doors are the engine thrust reversers. You can see them deploy together with the spoilers after landing in this video:

In fact, you can also see deployed spoilers in your picture, therefore excluding that it shows a takeoff.
The Coandă effect is used by the normal engine exhaust: by placing the engines above the wing, the exhaust flows over the upper part of the wing, and the Coandă effect causes it to follow the wing's curvature.

I did wonder about that. Can't watch the video right now. Is there a clam shell below the wing, as well?

@FreeMan It doesn't look like it. I wonder if this is enough to re-direct all bypass flow. Maybe some of it is still exhausted backwards.

A "blown flap" generates much more extra lift than simply directing the thrust downward. It allows higher AoA without stall and boosts circulation (which boosts lift) at a given AoA.

And a blown flap is what this is. Even with the very loosest interpretation, it isn't really the Coanda effect. That will just mislead you as far as how the STOL characteristics are being enhanced here.


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Why is the FOV of the Synthetic Vision of the Prodigy Flight Deck asymmetric?
Why is the FOV of the Synthetic Vision of the Prodigy Flight Deck asymmetric?
I am just reading through the manual of the Prodigy® Flight Deck 100 and came to the chapter about the synthetic vision. The document states:

[...] The field of view is 30 degrees to the left and 35 degrees to the right. [...]

Source (Page 510)

What is the reason and what are the advantages of having such a FOV with 30° to the left and 35° to the right?

Can you summarize the portion of the manual related to this feature instead of sending people to the 688 pages document?

Just a quick guess, but perhaps it reflects the field of view of a pilot in the left seat.

Seems to be that the PFD center is not at the center of the screen, leaving more space on the right, hence the resulting dissymmetry.


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Why is there a grid below the antennas of an VOR?
A few days ago I made a trip to the VOR-DME near my local airport LOWG, because I always wanted to see one. It's GRZ on 116.2.
When I was there, I wondered why there is a giant metal grid under the actual antennas of the VOR.

Source: Klaus Krasser
Close picture:

Source: Klaus Krasser
The grids squares have a size of estimated 10x10 centimeters.
What is this grid for? Is it maybe used as a shield or reflector? 116.2 Mhz has a wavelength of ~2.6 meters, so the grid would reflect the radiation. If thats the use of the grid, why is it needed?

VOR uses Alford loop antennas. Half the power of the VOR is directed below the antennas, this creates scattering. Additional theory. The ground plane prevents "VOR scalloping" due to multipath signal.

It's a ground plane https://en.wikipedia.org/wiki/Ground_plane

I would imagine the main reason is to make the performance of the antenna system more predictable and consistent.
Many antennas systems need a ground reference. All antenna systems are affected by nearby conductors. Using the grounds surface as your ground reference has a few issues.

It means your antenna system is at ground level. That means any nearby structures can potentially interfere with your signals.
The conductivity of the ground is weather-dependent. This would make the performance of the antenna system weather-dependent.
Speaking of obstructions you have to put all the electronics somewhere. You don't want a cabin sitting right next to your ground level atenna but you also don't want long feed cables between your antennas and your electronics.

By lifting the system up off the ground and using a metal mesh as the "ground" reference issues with obstructions and varying ground conductivity are avoided.

I think this is an example of a counterpoise:

[It] is a network of suspended horizontal wires or cables (or a metal screen), used as a substitute for an earth (ground) connection in a radio antenna system (...) when a normal earth ground cannot be used because of high soil resistance or when an antenna is mounted above ground level.

Generally used for LF and VLF antennas as that is where they are most efficient.
An example from that Wikipedia page of an AM radio antenna counterpoise:

I believe it's also the same principle that lets the antennas on the airplanes themselves, or on your car work.  Though when it's a solid piece it's referred to as a "ground plane".

oh, and thanks for the edit @ymb1 - much better. I should have done that myself :-)

@Perkins At least in amateur radio, things like this are often called ground planes too. In my experience, "counterpoise" mostly refers to a single wire used as a ground plane.


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Why do propeller blades not have winglets?
On the first look this question might sound ridiculous and maybe it is.
But as propeller blades act by the same physical laws as wings, and winglets reduce the induced drag by quite a bit, then why are they not put on propeller blades?
I could imagine that it might be a material problem. But are there any more reasons? And why exactly might it be a material problem?

I don't know but there are a couple of ways props are unlike wings: 1. considerable longitudinal tension. 2. moving through wake of prior blade, not clean air.

Related if not duplicate

Id say related as I'm not talking about a ring but actual winglets ;)

Propellers often have a very high aspect ratio to start with.

There are a few pictures on the Internet. Generally, the owners are not happy about their proplets.

@SimonRichter this is actually why I though about it xD

I flew a Piper Navajo PA-31-350 with "Q-Tip" props.  It helped reduce noise from the prop.

It's worth noting that propellers with 'wingtips' for marine use do exist. https://ing.dk/artikel/dansk-udviklet-energibesparende-propeller-solgt-til-man-dieselturbo-128613

Winglets on wings help because they increase the volume of air on which the wing can act. Extending the wing span would be much more efficient, but when span is restricted or the maximum wing bending moment is limited, winglets bring a small improvement in efficiency at high lift coefficients.
On propellers, however, the winglets would run through air which is already affected by the tips of the propeller. No additional air will be involved, so no efficiency increase will be possible. Please note that propulsive efficiency is increased by accelerating more air by a smaller amount. The formula for the propulsive efficiency $\eta_p$ of an air breathing engine is
$$\eta_p = \frac{v_{\infty}}{v_{\infty} + \frac{\Delta v}{2}}$$
where $v_{\infty}$ is the speed of the inflowing air and $\Delta v$ the speed increase of the air affected by the propeller disc. A smaller $\Delta v$ acting on a higher mass flow makes the engine more efficient. This effect is most pronounced when $v_{\infty}$ is low.
The prop tip winglets would operate in a region of high dynamic pressure and generate more friction drag without contributing to the prop's efficiency.
Things become different when the propeller blades have a very low aspect ratio and there is a hard restriction on propeller diameter: This is true for ships, where draught puts a hard limit on propeller size. Here a sort of winglet does indeed help: The Kappel propeller has its tip bent forward and increases efficiency by 3 - 6 percent. Given that marine propellers even for large ships have efficiencies between 50% and 60%, this is a noteworthy increase in efficiency.
By the way: Whoever tells you that winglets reduce induced drag quite a bit has something to sell to you, but I digress.

Pretty much everything that comes up when I google "winglets" says they're there to reduce energy losses from wingtip vortices. Do you have any links that analyze them from the perspective you're stating, and that weren't written by you?

@user2357112: Ask yourself: Can the vortex forming behind the wing still cause drag? Is there any mechanism which allows it to hold the aircraft back? Next: Don't read Wikipedia, the Web's collection of politically correct opinion. Don't read blogs and run away from short news articles: Their authors have no idea what they write about. Instead, look at scientific studies. PDFs of 30 or 50 pages. Light reading: Maughmer's article.

Can you link such studies?

The link you provided doesn't seem to support your claim: "In essence, the improvement in aircraft performance due to winglets results from their ability to reduce induced drag traded off against their added wetted area increasing the profile drag"

@user2357112: Take your time, read the whole article. BTW, why would that not support my claim? What do you actually understand my claim to be?

The last sentence of your answer strongly implies that the purpose of winglets is not to reduce induced drag. The article seems to contradict that. Your claim has other aspects that may or may not be contradicted by the article; I'm still reading.

@user2357112: My objection is to the "quite a bit" part. Read also the first paragraph, not just the last sentence. Winglets help at high lift coefficients and improve L/D by single-digit percentages. Read Maughmer: At high speed they are adding drag, at low speed they help. A bit, not "quite" a bit.

Still reading. The article is now talking about how winglets reduce the energy wasted in producing spanwise flow that ends up going into wingtip vortices, and how induced drag can be calculated by determining the energy contained in the trailing vortex system. "To minimize this drag, the amount of energy used in producing the required downwash must be minimized, that is, the energy that is “wasted” in creating unnecessary spanwise flow and in the rolling up of the tip vortices must be minimized." To a rough approximation, it's not that wingtip vortices cause induced drag...

...it's that the mechanism of induced drag dumps the wasted energy into wingtip vortices.

While the improvement in overall L/D ratio is only a few percentage points, and not at all speeds, the reduction specifically in induced drag appears to be quite substantial. The difference appears to be due to a combination of the increase in profile drag and Amdahl's law - reducing a part of the drag substantially can only reduce the overall drag by however big that part was.

@user2357112: At optimum L/D, induced drag is half of total drag. And again: If you spend the added profile drag on a span extension, your gain in induced drag reduction is 2.5 times bigger. Whatever you think is substantial, this is substantialler. See here for a meta study on winglet performance.

@sanchises: You are wrong. If the prop-winglet would increase lift locally, it would distort the lift distribution and increase induced drag for the same lift. If you need more thrust, increase RPM! I hate it when people down vote an answer simply because they did not understand it.

This answer is wrong! Winglets on a prop would limit spanwise flow, leaving more air to work on. Furthermore, winglets can be designed in such a way so as to suck air inboard towards the prop hub, further increasing the air being worked on, they would also reduce induced drag from tip vortices. Because of the strong outboard flow along the prop, there is also air circulation from the bottom to the top surface which significantly reduces lift on the prop tips because the high pressure air from the bottom ends up in the low pressure region on top, proplets would reduce this.

@MishaP … that's why we see winglets being added to props all around, don't we? If you think you know better, don't just put unproven claims in a comment but write a better answer.

@PeterKämpf Many things that improve airplane efficiency are not in productions for a variety of reasons. For instance, why don't we see blended wing or prandtl wing airplanes? Wing tunnel and homebuilt experiments have confirmed the theory, but companies such as Boeing, Airbus, etc, do not want to risk millions and/or billions on such radical changes. A sausage with wings flies well enough, why take risks? On top of that - sometimes manufacturing costs are too high, or technology does not exist to reliably implement theory. So the claim "they don't exist, so it's inefficient" is false.

@MishaP: Blended wings are pure marketing and Prandtl wings fly all around you, only not by that name. All and more have been studied intensively and only the designs that work have been built. Do you really think the engineers are that stupid?

Engineers - no. Marketing, execs etc, that are happy to keep selling old stuff as long as it sells? yes.

@MishaP: I agree, but what they sell is not old stuff. It might seem that way because we have arrived at an optimum and can improve this only very gradually. All radical departures lead downhill.

@PeterKämpf most notable "radical departures" that lead downhill were attempted when technology was significantly less developed than it is now - no composite materials, no CFD or FEA analysis, and many many more advances that have been made since then.
A great example - canards were deemed statically unstable, until Burt Rutan made then long ez which is statically stable. Fighters solved the issue with electronic stability augmentation. However, still no canards on commercial airplanes. Just one example.

@MishaP: Where did you get that nonsense from? Of course were canards considered as stable as conventional aircraft. See Focke-Wulf 19 Ente or MiG 8 Utka. Just because the Wrights didn't get stability and Rutan is a blowhard? But nobody sane wants to fly with those spoilers up in front.

@PeterKämpf both the FW19 and Mig8 showed unstable behavior. I've lost interest in this discussion. goodbye.

Hartzell make propellers that appear to have winglets (tips bent aft) called Q-tips. The name seems to refer to them being quieter. I have read that they do the same job as a slightly larger diameter prop. They seem to have no life issues. Since noise costs energy, and a smaller prop does the same job.... it is possible that they are more efficient. The bent tip is small - on the order of a couple of inches.

It's my understanding that the bent tip helps reduce the air pressure immediately outboard of the propeller, not unlike a winglet.  This does two things: keeps the pressure inboard, where it can add to the propulsive thrust, and reduce the ability for sound to propagate outwards.  So, yes, it would make for a quieter prop.  But that's just a side-effect; the main effect is improved efficiency of the prop.  And no, it doesn't need to be big; the ratio of winglet to wing is pretty small so the ratio of bent tip to propeller radius would be pretty small, too.

Strange that increased sweep at the tip of a wing/prop is now called a winglet with much more frequency. Along these lines - there are scimitar and other form factor props that have similar benefits.

Pros:

Winglets on a prop would limit span-wise flow, leaving more air to work on, because it does not "fly away".
Furthermore, winglets can be designed in such a way so as to suck air inboard towards the prop hub, further increasing the amount of air being worked on.
They would also reduce induced drag from tip vortices. Anyone who says winglets are trash can explain that to all competitive gliders, Boeing, Airbus, Cessna, and any other modern aircraft manufacturer, most of whom use some sort of wingtip device.
Because of the strong outboard flow along the prop, the low pressure air from the top of the blade, and the high pressure air from the bottom of the blade both end up outboard of the propeller, where the low pressure region sucks high pressure air from the bottom of the blade onto the top, thereby reducing the high pressure on the bottom, and increasing the low pressure on top, resulting in a completely useless portion of the blade, which produces very little thrust but still creates drag, and requires more power to turn the propeller.

For all of the above reasons, a propeller of the same diameter that is placed into a shroud can potentially create up to 85% more thrust using the same engine, as a propeller that is not shrouded.
Cons:

A wingtip located on the tip of a propeller would be constantly accelerated outboard, if a regular propeller blade deals with this acceleration rather easily, because it is an axial load on the blade, the winglet would be a cantilever beam, and the forces would rapidly add up creating a rather formidable force on any significantly large winglets on the tip of a propeller.
Besides the magnitude of the force, and the fact that it is a cantilever type load, it is also a variable load which is less on low RPM, and higher on high RPM, which quickly leads to material fatigue and structural failure.
The cost to manufacture such a propeller would be higher.
The weight of the propeller would be higher to account for the structural loads listed above.

Boils down to cost, weight, reliability.

Winglets on propellers look like propellers that have gone through "ground strike" and the FAA grounds prop-driven aircraft with propellers damaged due to ground strike.
It's simply more expensive to manufacture, certify, and maintain; even though it does provide improved thrust in take-off position; but potentially more drag during cruise and feather conditions (based off propeller pitch, will be different with different propellers).
BERP tips most likely more effective overall considering take-off, cruise, and feather conditions (feather is the desired pitch during engine failure to prevent wind-mill and drag from the prop free rotating).

your first paragraph does not really sound like a good reason, the FAA would know which models use those props.

Simon Richter mentioned in his comment that pictures of ground strikes are readily available online. I'm going to go out on a limb and say that even FAA investigators would be familiar with what a ground strike looks like and with the design of proplets and be able to tell the difference.

The concept of 'winglets' was applied in early days of aviation by the inventions of Henri Coanda, patents: 1937GB191112740, 1910; CA370885, 1937; and to boat propellers; you can have a look, also in ESPACENET, at patents: ES-0444150, Inventor: 'Gonzalo Perez Gomez', and ES-8300608, 1987, same; and ES-0293837_U by 'Ramon Ruiz Fornella', all from: 'Astilleros espanoles'.
'NASA Technical Memorandum 87771', by Milton A. Beheim: 'NASA Research in Aircraft Propulsion', shows a propeller with 'winglets'.
I'd say that one of the reasons for winglets in wing tips is to reduce the marginal vortex, due to the compensation of the difference in pressures between the upper and lower surface of wing, this 'vortex' or 'swirl' increases drag, and thus impairs overall airplane efficiency.

There has been much research into winglets. early on they were not considered effective, however, I challenge you to find a modern commercial plane without winglets, and that's because they improve overall airplane efficiency. To say otherwise is misleading.

The same reason why there are no winglets on gliders. The majority of propellers tips are small & pointy enough that there is a negligible spillover to cause wingtip vortices that makes the wing inefficient. Prop blades with wide tips like the ones in C130's  or Huey helicopter blades may be improved with winglets but such design also adds complexity(cost), weight and forces that may impede the reliability & safety the blades.

almost all competition gliders have winglets

Be careful not to upset the members of the winglet cult, for they are easily irritated and punish you with downvotes if you don't share their beliefs.

A Huey helicopter blade is not a propeller: it is a rotating wing (airfoil).  Helicopter blades on a great many models improve performance (and reduce noise) around the tip by sweeping the tip back.    The constantly changing air flow over a rotor blade in flight is significantly different from the airflow over a swept wing airliner. This answer was down voted due to misinformation.

authors: Елена Кесафоти


text:
Is it possible to use reverse thrust while airborne?
I play a flight-sim called X Plane. The other day while I was approaching an airport a little too fast and knew I couldn't slow down in time. I decided to use the reverse thrust while I was still in the air and this helped dramatically and I was able to land safely.
But now I'm curious - Would using reverse thrust in a real-life Boeing 747 have the same effect, would it cause the plane to crash, or go out of control?

This was the first thing to come to my mind.  It could stall the airplane near the ground, resulting in a crash. https://www.youtube.com/watch?v=WKCl3lfAx1Q#t=132

Flying with reverse thrust reminds me of this: https://www.youtube.com/watch?v=6YkkZw9GVaU

The space shuttle had such a low L/D profile that it was simulated by a jet flying with the thrust reversers deployed. http://en.wikipedia.org/wiki/Shuttle_Training_Aircraft

This might be interesting to take a look at: https://www.youtube.com/watch?v=Yq5HLtdGeqE

also take a look at: https://www.youtube.com/watch?v=Gdn0465zE4o

Commercial jets are not designed to use reverse thrust in flight. With engines mounted under the wing, the turbulence can affect the lift over that section of wing. Tail mounted engines could interfere with the tail. This, in addition to the huge increase in drag, is what causes loss of control, as in the incidents that RedGrittyBrick mentions. Speed brakes are designed to provide the needed drag for emergency descents or otherwise slowing down faster. If the pilots find themselves too high/fast for an approach, and deploying spoilers/gear/flaps won't fix it, then they should go around for another approach.
The loss of control is more of a risk when a thrust reverser deploys only on one engine. Other risks are still there, since those thrust reversers are designed to deploy in landing conditions, not flight conditions. Notable exceptions listed on Wikipedia include the Hawker Siddeley Trident, though it also mentions that the capability was not often used.
Military aircraft, such as the C-17, can be different. They tend to make extremely steep descents more often (called a tactical descent/approach), so thrust reversers can be used in flight.
I did some testing with the stock 747-400 in X-Plane. Deploying the thrust reverser only changes the force applied by the engine, but doesn't seem to affect the air flow. So the loss of lift is not reflected by the model.

It was years ago, but I was on a DC-8 that had been re-engined with turbofans.  On this flight, they used reverse thrust in flight to lose altitude quickly.  The Captain came on the intercom first to warn the pax of an unusual noise and vibration before he did it, and then he used the reverse thrust.  Yes, it was noticible and a bit noisey in the cabin.  I am glad he gave the pax warning.  Concerning the pax may be a reason why this is generally not done, even if the plane is capable of this maneuver.

years ago I saw a 747-200C use TR in flight during final approach to rapidly descend when it crossed the runway treshold way too high. Yes, it happens but it's rare. I think I've also seen incident reports of accidental TR activation in flight but that memory is very vague.

It may depend on the aircraft and situation but an unintended deployment on one engine lead to the in-flight break up of a 767

At approximately 15 minutes into the flight and at approximately 25,000 feet altitude, one flight crew member commented that the reverser had deployed.
  This comment was immediately followed by evidence of a rapid airplane attitude change and subsequent in-flight break up, leading to airplane wreckage falling into remote jungle terrain approximately 94 nautical miles from Bangkok.

Thanks for the link, I actually just finished reading about that same flight on Wikipedia.

The Pilatus PC-6 (a turboprop) can be put the prop into reverse pitch and descend nearly vertically.  Here's a demo https://www.youtube.com/watch?v=PU3RecxHRtk

Note that the question is tagged boeing and boeing-747, so this answer doesn't really apply.

No it doesn't apply at all, but if the goal is to teach people about the topic of reverse thrust while airbone, I think this does a fairly good job.

Well, as you know, the goal on this site is to answer the specific question that was asked instead of trying to answer variations of it.  :-)

As Skip Miller Mentioned the DC-8 thrust reverse was designed for in-flight operation.
Skip Miller:

It was years ago, but I was on a DC-8 that had been re-engined with
  turbofans. On this flight, they used reverse thrust in flight to lose
  altitude quickly. The Captain came on the intercom first to warn the
  pax of an unusual noise and vibration before he did it, and then he
  used the reverse thrust. Yes, it was noticible and a bit noisey in the
  cabin. I am glad he gave the pax warning. Concerning the pax may be a
  reason why this is generally not done, even if the plane is capable of
  this maneuver.

DC-8 Manual ,American International Airways, page 29

Descent rates of less than 4000 ft/min are sufficient for all normal
  Operations. A descent rate of 1 000 ft/min is about maximum that Will
  allow a precise comfortable Level off. This should be closely monitored
  when within 2 000 Feet of the ground. Reverse thrust, if necessary,
  may be used in normal descent at speeds above 1 90K IAS. When this is
  done it is limited to inboard engines only.

Lauda Air Flight 004 (NG0049) overview:

  Some thrust reversers were designed for limited use in flight (such
  as inboard engines on the McDonnell Douglas DC-8)


text:
Russian-built and NATO (USN, European) probe-and-drogue -- are they interoperable?
Considering the current diversity of coalition air fleets in some parts of the world (the Horn of Africa situation comes to mind), can Russian-built tankers refuel NATO probe-and-drogue receivers, and vice versa? (Say, a US Navy F/A-18E getting a helping hand from an Indian Air Force Il-78MKI, or an Ethiopian Air Force Su-27 filling its tanks from a Royal Australian Air Force A330 MRTT?)

The drogue system was standardized in the 50s and reverse engineered by the USSR in that time so nearly all aircraft that use it are compatible with each other.

Flying boom does not come into this question at all. The question is whether NATO probe-and-drogue is compatible with Russian-built probe-and-drogue.

This answer would be a lot clearer if you removed references to the flying boom

What probe-and-drogue aircraft are not compatible with the NATO system?

Can Russian-built tankers refuel NATO probe-and-drogue receivers, and
  vice versa?

The Russian system is called UPAZ and its manufacturer Zvezda states

The nozzle assemblies are adapted to the refueling pods of foreign aircraft

http://777.zvezda-npp.ru/engl/zaprav.html
Basically this means a bog-standard Russian Mig/Sukhoi cannot plug into a Western tanker aircraft without some change in the configuration.

Say, a US Navy F/A-18E getting a helping hand from an Indian Air Force
  Il-78MKI

The Indian IL-78s have Israeli-made refuelling equipment so I can't say whether it's compatible with F/A-18E. However, from what I know, India has been using this Israeli equipment to refuel its MiGs and Sukois just fine.


text:
What's a Class F cargo compartment?
Apparently, the Aviation Traders folks worked with EASA to define a special type of cargo compartment, known as a class F, during their work on Iron Maiden's touring airplane.  Just what is a Class F cargo compartment, and how does it differ in safety properties from the large class B compartments used on earlier combi configured aircraft?

Here in this amendment to the EASA CS-25 it says on page 4:

... for a new Class B cargo
  compartment definition as well as design criteria for a new Class F cargo compartment
  type. This latter class of compartment was introduced because whilst it was concluded
  that manual fire fighting was not feasible for larger compartments, alternatives other
  than just the existing Class C were identified.

And a bit further on page 5 (emphasis mine) :

... Further, a new Class F cargo
  compartment definition is added, which is not limited in size and which provides the
  means to control or extinguish a fire without requiring a crewmember to enter the
  compartment. This proposed Class F compartment standard accommodates the carriage
  of large amounts of baggage and cargo loads on Combi aeroplanes as well as in
  compartments of smaller sizes exceeding the new Class B definition. New aeroplanes
  designs can take advantage from the variable solutions under the Class F definitions to
  ensure an acceptable level of fire protection.

And more concrete:

The AMC further provides guidance for usage of other fire
  protection means in the new Class F compartment such as Fire Containment Covers
  (FCC) or Containers rather than having a liner installed to contain a fire and to protect
  the critical systems and structure of the aeroplane.

I guess it's meant to allow storage of cargo in non-cargo areas (which do not have the adequate fire protection measures such as liners) if other non-traditional measures are installed (such as the Fire Containment Covers)


text:
How are type ratings created for new aircraft types?
When a new aircraft is developed that requires a new kind of type rating to fly, considering that FAR 61.195(b)(2) and (e) require the instructor giving a type rating (or any sort of instruction) in an aircraft that requires a type rating to hold a type rating in that aircraft, how is the first type rating for that new aircraft type issued?  Is it implicitly acquired by the flight test pilots, who then can give type rating exams and checkrides to other instructor pilots?  Or is there some procedure tucked into a dark corner of FSIMS that is used when "we need a brand new type rating, now what?"

Seems you guessed right, actually.  FSIMS 5.9.3 does indicate that you can get a letter of authorization in lieu of a type rating:

B.    Requirements for Aircraft Undergoing Certification. During the type certification process, it is sometimes necessary for industry pilots or FAA inspectors with airman certification responsibility to be qualified in a particular aircraft before a pilot certificate type rating designator is established for that aircraft. In these circumstances, and at the discretion of the manager of the aircraft evaluation group (AEG), an LOA (Figure 5-187) may be issued in lieu of a type rating. This LOA and Letter of Application (Figure 5-188) must be in the pilot’s possession when exercising the authorized privileges. The LOA can eventually be surrendered to a district office in exchange for a temporary airman certificate bearing the category, class, and type ratings.

Which CFI gave Orville his endorsement to solo, anyway???  Sometimes the first ones just get the benefit of slightly different rules that the rest of us follow.  And for purposes like this, that's probably inevitable.


text:
Non-precision approaches for which constant descents are not approved?
I noticed an interesting note -- circled in red pencil below -- on the KEEO RNAV (GPS) RWY 03 approach the other day:

Why would the FAA apparently prohibit constant-descent final approaches to this airport, given the operational benefits they provide to aircraft of many types? (While props can get away with a lot more on approach than a jet can -- diving and driving is still more workload than maintaining a constant descent.)

Without hunting for more details, I suspect that it's highly mountainous terrain, and the ridge(7000') between WAGOK and the runway might be too close for decent obstacle clearance.

Your MDA is well above the ridge east of WAGOK, and WAKOG protects you from the ridgeline right under the FAF.  Inside WAGOK you're good down to the MDA as fast as you can get there, so lack of a published descent angle shouldn't be driven by terrain at/after WAGOK, as far as I can tell.

@slookabill: You do realise that that ridge isn't much higher than the runway itself (6415'), right?

Probably because it's so shallow: you have 8+ NM to descend about 1100'. On a 3 degree angle, you'd typically decsend 1100' in a little over 3 miles.  I'll leave it to good folks with calculators to work out exactly what angle this would be, but it's under 1.5 degrees, so probably below whatever limit TERPS gives for depicting an angle there.
One solution would be to remain at the FAF altitude until reaching a calculated "fly-off" point, at which time you would descend at a 3 degree angle until reaching published MDA + 50', at which point you continue or go around.  But that probably takes specific FMC software & perhaps a tailored approach chart, so with only this one your option pretty much looks to be "dive" (not that far) "and drive" (quite a bit).
Though that gets you to an MDA that is 1700'+ above the TDZE...
ACTUALLY, ON FURTHER CONSIDERATION: It isn't too shallow, it's a steep path from FAF to TDZE, 3000' in 8 NM (would be 9NM at 3 degrees). And the angle to do that probably doesn't quite clear the WAGOK step-down, meaning your vertical path becomes even steeper at that point than it starts out.
So rather than publish gradient***s*** steeper than (whatever the TERPS limit is), and increasing after the step-down fix, they just say NA & let you "make it work" on your own.
I notice that there is no VDP published here, either...


text:
What aircraft design elements contribute the most to sustained flight?
If I wanted to design an aircraft for autonomous operation and maximum endurance, what design philosophies provide the greatest benefit?  I'm imagining a powered glider.  Does not have to be highly maneuverable.
I'm interested in relative proportions, wingspan, length, center of gravity, center of pressure, wing placement, dihedral/anhedral, engine placement, fuel type, etc.

Is there a "sweet spot" for center of gravity relative to center of lift so as to maximize stability?
Since it will be mostly autonomous (computer-controlled), can I design for less inherent stability?
What engines/fuel types are the most efficient?

What kind of an aircraft are you thinking of? In what ways might it be similar to and different from a Reaper, say?

the reaper is a good starting point, at least in terms of using it as an example for why the design looks like it does.  i was thinking something more in the tactical realm, perhaps no bigger than 15-20' wingspan, or something hobbyists could put together on the weekend.

A balloon :-). ${}$

What exactly is a powered glider? Do you mean a motor glider that has an engine for take-off only?

@RedGrittyBrick there are a number of different kinds of motor gliders: self-launching (instead of a tow or winch), sustaining (in case you fail to find lift), and touring (can operate like an airplane).

The best approach you can use is to select a similar aircraft and start from that design adapting to yours. From what you say maybe the Predator UAV is your best option, taking that design just iterate the design by removing military systems. Scale it back to the payload you need. Copy/Paste is usually the best option generally.

Don't use a configuration that was selected to be transported in a torpedo tube and then made to behave the hard way. It will be better to start with something that was designed to fly stable all by itself.

@RedGrittyBrick it could be, only the motor would be left on all or most of the time instead of switched off/stowed at altitude.  but i'm also open to alternative technologies to produce thrust, so i left it as simply "powered".

Natural stability would be highest on the list for me. Look at free flying model airplanes for inspiration. They have their own characteristics:

Very low wing loading for minimum sink speed
High natural stability, and consequently a very narrow speed range
High aspect ratio wing, thin airfoil with high camber
Extremely short fuselage ahead of the wing (no payload to carry)
Extreme fuselage length aft of the wing which provides ample aerodynamic damping
Strong dihedral of the outer wing.

This in combination means that your control software can be very simple. Relaxed stability will require many sensors and built-in redundancy, and the more parts you need to add, the more possibilities of failures you will end up with. In contrast to that, the laws of physics never fail, use them to your advantage. See below for an example which I copied from the Wikipedia page on free flight models:

For airfols, c.g. location and all other details I recommend to look at several free plans until you see a common pattern.
Regarding the type of fuel: Depends how noisy and messy you tolerate the engine to be; some people will only fly electric while others are happy with two-stroke engines.


text:
Are there left seat qualifications specific to actual handling of the aircraft?
The following three posts explain that both yokes and side-sticks require changing the hand that holds the yoke/side-stick when switching seats:

Why are Airbus captain control sticks placed on the left when most people are right-handed?
Are there risks if the side joystick must be handled with a pilot's weaker hand?
Do some right-handed pilots fail to use the left stick of an Airbus?

I can imagine at least some difficulty for a newly promoted captain having to essentially re-learn everything (handling wise) from the left seat after logging thousands of hours from the right seat (regardless of the dominant hand).
So, what are the minimum qualifications for progression from right to left seat when it comes to handling the plane? Is there extra training involved? Does a left seat pilot hold extra qualifications for handling the plane?
Or is this a non-factor?

Not exactly dupes but you may find what you are looking for here and here

@Dave thanks, I had read both of those -- perhaps it's a non-factor, but curious if there were actual minimum quals involved.

The qualifications will depend on the country and the airline. And switching hands isn't specific to Airbus, see here.

Moving to the left seat of almost any aircraft involves the transition from flying with right hand on the yoke & left hand on the throttles to now flying with the right hand on the throttles & the left hand on the yoke.  The Airbus only differs in that that outboard hand is on a sidestick instead of on a yoke.  After a few hours of getting used to flying with your other hand, it's no big deal.

@ymb1 yokes at least allow for ambidexterity in handling the aircraft while in flight during all phases/levels of training and overall experience, whereas side sticks do not, limiting the pilot to use only the one hand (determined by his seat position).  that was the main thrust of my question, but i do like your edits, and i think it makes for a better question.  thanks!

No, it is a non-factor, although in the Navy there are aircraft you only conduct carrier landings from in the left seat. To be qualified as an instructor in that aircraft, you have to demonstrate the ability to fly the same pattern from the right seat (but not actually land on the carrier).
I'll tell a story about switching hands. I was an LSO (landing signal officer) for E-2s, which had yokes and a central throttle quadrant. You always flew the carrier approaches from the left seat, though.
We had a pilot who had developed bad habits in the landing pattern. To break him of it, I had him fly the landing pattern from the right seat at the field, which just plain felt awkward since you never did it at the boat. This made him break out of the auto-flying and have to think his way around the pattern instead, and he was able to stop what he was doing wrong. He carried the fix back over to the left seat.

I updated to answer the question.

It's a non-factor.
At this point in their careers, pilots have logged so many hours both in the left and right seat, that they have become ambidextrous during operation. I've never heard of this process being so inconvenient or difficult as to cause a mishap or prevent a person from typing in an airplane.
Curiously the military tactical community does not share that belief and utilizes right hand control of the aircraft only. In the B-1 and B-2 bomber aircraft, for example, there are separate throttle quadrants for the pilot and first officer, so each crew member can control the stick using the right hand and use the left hand for throttle control.

(ww2aircraft.net) B-1 cockpit

A B-52 bomber is about as tactical as a B-1 bomber, and it has a traditional central throttle quadrant.

When I learned to fly I did all my flying from the left seat (as is typical).  That means handling the yoke primarily with your LEFT hand, while throttle, radio etc with your right.  When I was getting my CFI, I was a little worried about the transition to flying from the right seat.  For me it was a non-issue.  The hardest part was the change in view (judging where the runway center-line is from the right), but even that was non-issue.


text:
What is the horizontal and vertical fields of view for a VASI and a PAPI approach system as you come in to land?
As you come in for landing, at what angles should the VASI or PAPI lights be visible on the approach in the Horizontal and vertical planes. {E.G. 30 degrees horizontal and 20 degrees vertical}

The only thing I can find in the AIM (Chapter 2, Section 1, 2 (a)) is for the VASI and it says +/- 10° from center line, I can't find anything that says the maximum angle above the glideslope, but usually the angle below the glideslope you can see it extends to the ground (drive by an airport, you'll see all reds).

If there are technical specifications defining this (for the FAA), it will almost certainly be found in Appendix E of this document. No time to do further research right now; someone else can go for it.

This information is for the US, taken from FAA Order 6850 - Visual Guidance Lighting Systems.

VASI (2 bar VASI for illustration, but other configurations exist)
a. Layout

b. Aiming

The two-bar VASI system shall have the upwind bar aimed at three
  degrees and the downwind bar aimed one-half degree lower at 2.5
  degrees; however, where necessary to provide obstacle clearance, the
  downwind bar may be aimed at 2.75 degrees.

c. Glide (vertical) path angles

d. Horizontal field of view: 10°

Determine the minimum aiming angle by plotting all objects within an
  area  established by two lines each diverging at 10 degrees from
  runway centerline extend to 4 nautical miles, and starting at the
  runway centerline at the number one bar.  A line drawn from the runway
  centerline at the number one bar at an angle that will clear the
  highest object by not less than one degree establishes the minimum
  aiming angle.  This line and a horizontal line perpendicular to the
  runway centerline at the number one bar (downwind) establishes an
  obstruction - clear plane 10 degrees (6 degrees in special
  applications where 10 degrees is not obtainable) on both sides on the
  extended runway centerline.  The obstruction clear plane starts at the
  number one bar and extends outward from the threshold for four
  nautical miles.  In addition, the minimum aiming angle shall be within
  the glide path limitations of paragraph 4. When less than 10 degrees
  are used for determining the obstruction-clear plane, issue a NOTAM
  and request publication in the Airport/Facilities Directory.

PAPI
a. Colocation with ILS glideslope

When siting PAPI on a runway with an established electronic glide
  slope, the PAPI visual approach path should coincide, as much as
  possible, with the one produced electronically.  To accomplish this,
  the PAPI is placed at the same distance from the threshold as the
  virtual source of the electronic glide slope within a tolerance of ±30
  feet (±10 m).  The PAPI is aimed at the same angle as the electronic
  glide slope.

b. Layout

c. Aiming

The visual glide path angle is the center of the on-course zone, and
  shall normally be 3 degrees when measured from the horizontal.

d. Glide (vertical) path angles

e. Horizontal field of view: 10°

The PAPI obstacle clearance surface is established to provide the
  pilot with a minimum clearance over obstacles during approach.  The
  PAPI must be positioned and aimed so that no obstacles penetrate this
  surface.  The surface begins 300 feet (90 m) in front of the PAPI
  system (closer to the threshold) and proceeds outward into the
  approach zone at an angle 1  degree less than the aiming angle of the
  third LHA from the runway.  For a 3 degrees glide path and 20 minutes
  separation between LHAs, the third LHA from the runway would be aimed
  at 2 degrees, 50 minutes elevation.  The surface extends 10 degrees on
  either side of the runway centerline extended, and extends 4 statute
  miles from its point of origin.  The surface is shown graphically in
  figure 5-4.  If a site survey determines that there is an obstacle,
  which penetrates the obstacle clearance surface and cannot be removed,
  then the glide path angle must be changed or the PAPI system moved
  further from the threshold.  By moving or re-aiming the PAPI, the PAPI
  obstacle clearance surface is repositioned so it will not be
  penetrated by an obstacle.


text:
Can you help me identifying an A-4 Skyhawk-like jet?
I'm having trouble identifying a jet and am hoping someone can provide some help.  Here is the best picture I've been able to capture.

The closest similar jet I've been able to find is the A-4 Skyhawk, which shares many of its features, but even in looking through the variants, I can't find an exact match.
The next two pictures aren't as clear, but they show the profile and wing shape, respectively.

There are three features I've noticed which set it apart from the A-4 variants I've found.

Wing shape - It's very curvy, almost Concorde-like.
Vertical stabilizer - The forward section of the top of the vertical stabilizer is very sharp, whereas on the A-4's I've seen, this is curved.
Antennae - There are two antennae; one swept-back antenna directly behind the cockpit and a vertical antenna farther back where the vertical stabilizer begins.

I appreciate any guidance you can provide.  Thank you.

Later-model A-4s (H+, maybe earlier?) had a squared off tail. Antennae aren't the best way to distinguish aircraft, fwiw, as they can be easily added or removed later in life.

They are A-4 Skyhawks all right. They are operated by Draken International and provide adversary training for USAF (among others); here's a closeup photo of them.

Image from edwards.af.mil

That is indeed it.  Thank you for your thorough answer.

For completeness, the two depicted appear to be a TA-4(?) and an A-4M: that hump in the back (the one on the right) is a distinctive feature of the A-4M (aka Mongoose IIRC).

Those are Draken International A-4K KAHU Skyhawks, based of of Lakeland regional airport. They have 8 or 9 of them, unfortunately, one was lost last year outside Las Vegas. They are former Royal New Zealand Air Force strike fighters.
These are not your typical A-4 Skyhawk - they are true wolves in sheep's clothing. They have the HOTAS, MFD, radar, and war computers of an F-16 Falcon. Project KAHU was undertaken in late 1980's to early 1990's. All of New Zealand's Skyhawks had their air frames zeroed and then brought into a generation 3+ strike/fighter, almost a 4 a few weapons shy. However with a software upgrade they could have carried the AIM-120 BVR air-to-air missile. But she could carry all the other air to air or mud moving gear of the F-16.
The ones with a hump and tail extension were acquired from another contractor that was bought out by Draken. Those are H models from the IDF.

A-4K Showing the underside, with some Sidewinder and Maverick missiles.

All the assembled A-4Ks and TA-4Ks one T-Bird was lost.

A-4 Skyhawk over Christchurch, NZ

Welcome to Aviation.SE! This is good info! Please provide sources or citations for the photos.

Yes, welcome to Aviation.SE!! What does "almost a 4 a few weapons shy" mean? Looks like you were busy typing away and forgot to complete your thought.

@FreeMan: In context, "3rd generation, almost a 4"  probably refers to jet fighter generations

a generation 3 fighter is an aircraft like the F-4 Phantom, A-7 Corsair. Aircraft that have air to air and air to ground capabilities with active radar, active ECM and can carry a oat all weapon systems available to NATO or NATO friendly air forces. The A-4 K carried the same version of radar as the F-16.

It's the two-seat training version of the Skyhawk. You can see this in the photo:
there are two pilots seated in tandem.
According to the A4 Skyhawk Association, there were several two seat models built:
U.S. versions of the two-seat Skyhawk were the TA-4E, quickly changed to TA-4F, the TA-4J, and two special variants, the OA-4M and EA-4F.
Export variations of the two-seater were TA-4G {Australia), TA-4H (Israel), TA-4K (New Zealand), TA-4KU (Kuwait), TA-4PTM (Malaysia), and TA-4S (Singapore).
The ones shown above are probably the US version.

Any chance you could link a source for this?  It's not that I doubt you, it's just good to cite sources on questions like this.

Yes of course, added links. I am new here :)

Excellent!  Thanks!

Looks to be a pair of T-A4K Skyhawks carrying a center-line droptank


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Why do commercial airplanes smell like fuel smoke before take off?
Why does the cabin of commercial airplanes always smell like fuel smoke coming out from the internal ventilation a few minutes before taking off, I think when the pilot puts thrust into the engines before going to the runway?
A few days ago I went on a trip and noticed this too, when landing. Is it normal?
What is the reason to have the passengers smoked?
Thanks!!

Welcome. I don't understand the question: Do you mean why airplanes have a fuel smell before taking-off?

I don't know the term, but it's exactly what Dave answered bellow. Thanks everybody for fixing my grammar errors. I really appreciate the fixes :)

This is often a result of when the planes push back from the gate or if there is a direct tail wind on the ground. The pressurization system for aircraft uses bleed air from the compression stage of the engine. If the engines are running at push back or idling when a tail wind hits them the brief reversed airflow can cause some vaporous fuel to make its way forward in the engine and come through the air system causing the smell. This page covers it pretty well. Patrick Smith also touches upon it here.

Those links are VERY interesting. Thanks!

If you are interested in Aviation in general (as well as the topic here) Patrick Smiths book is a great read and pretty easy to get through (I just finished it).

It's extremely unlikely that flow would be reversed in the engine. The engines/APU are just ingesting exhaust/fumes from themselves or other aircraft that is blowing around the airport, or possibly oils leaking upstream in the compressors.


text:
Can a U.S. President have a non-government owned aircraft that would routinely be given the call sign AF1?
Can a US president use a personally owned jet with the call sign AF1? Would the Air Force be obligated to add security and defense measure to this aircraft if the president refused to fly in the VC-25?

Not really about aviation.

The premise of the question is about an aircraft, though it is hypothetical in nature.

Making this question more general might help it get reopened. The question about callsign seems on-topic. The question about converting other aircraft is pretty much covered here.

@DecKonroyd no, it's about a call sign, not an aircraft. None of the aircraft would "be" "air force one" if the president weren't on board, so no, there's never more than one AF1, and most of the time there isn't one at all.

The revision by @digitgopher improved this quite a lot. Voting to reopen.

Other government units have aircraft. I wonder what they would call it if he flew on a Customs and Border Patrol plane.

Air Force One is the call sign of whatever USAF aircraft (see @slookabill's comment below) the US President travels in. Once he boards another aircraft, the call sign AF1 is transferred to that aircraft (for a dramatic example of this, see the climax of Air Force One movie).
If a president were to fly in their own aircraft (or commercially) the appropriate ATC call sign would be Executive One.

As far as fitting out a personal aircraft, the VC-25s are USAF assets (operated by 89 AW) and are highly customised and specifically configured for the job of transporting the president (and support staff), costing over $300 million. I doubt any president is going to get the option of flying their favorite aircraft on a regular basis instead of the state aircraft.
It is not likely that the government would pay to configure another (non-USAF) aircraft for the president to the same specifications as the VC-25s serving as Air Force One. After all no US President's personal car has been configured as the Presidential State Car so far.

Technically, Air Force One, is the callsign if the president is flying an Air Force Aircraft. When he's flying with the Marines, it's Marine One(mostly the helicopters), when he's flying the Navy, it's Navy One. When he's flying commercial(and it's technically possible), it's Executive One.

@slookabill You're right.

Just as a matter of trivia, the tail numbers for the two VC-25s are SAM28000 and SAM 29000. SAM as I remember stands for Special Air Mission. Back in the Clinton days, they used to show up at Tel Aviv and preempt our usual parking area.

@voretaq7 Thanks for the correction.

Just to keep things in perspective, the modifications made to the VC-25s to make them the President's planes are not all that expensive; a new 747-8 right off the production line for practically any commercial airline would cost over $300 million as well. Now, if you're saying the Air Force spent an additional $300 million over the cost of the airframe itself, source?

@KeithS I'm not saying that the modifications cost $300m, rather the planes cost that amount. My point is that any President cannot simply say that 'I dont want that $300m aircraft, lets's customise my private jet and fly it instead.'

@aeroalias - Understood. Actually though, I looked it up, and a Politico report on replacing the VC-25s with new 748-based airframes (http://www.politico.com/story/2015/01/air-force-one-boeing-747-8-114689) puts the cost at $1.7 billion over five years. It's unclear whether that cost includes operation of the existing VC-25s while the new ones are built, but pessimistically it means each one will cost $850 million, making the mods to each $325 million airframe substantially more expensive than the plane itself.

Those mods include things like RWRs, missile countermeasures (flares/chaff/mirrorballs), EMP/radiation shielding of the hull and electronics, bulletproofing of the entire hull including armored glass windows, a custom cargo area with airstairs and ramps for a "Beast" limo, aerial refueling system, several secure satellite and ground-based communications links, all in addition to the luxury appointments of the passenger area.

Side note: George Bush once flew a "secret" mission to join the troops in Iraq for thanksgiving dinner. He flew on the VC-25, however the aircraft operated under a normal callsign, and filed it's flight plan as "Type: Gulfstream 5", in order to keep the mission a secret. They were almost rumbled over the UK, when another pilot contacted ATC, asking them if that was 'Air Force 1' below them. ATC replied saying no, that's a Gulfstream. It would probably have been far easier to just fly the president out on an actual G5, at least from a secrecy perspective, but they chose this way instead.


text:
would a dimpled heat shield reduce heat transfer during reentry?
Would a large ceramic golfball absorb less heat on reentry than a standard sphere?
"The difference in the flowfields around a smooth sphere and a rough, or dimpled, sphere can be seen above. Since the laminar boundary layer around the smooth sphere separates so rapidly, it creates a very large wake over the entire rear face. This large wake maximizes the region of low pressure and, therefore, results in the maximum difference in pressure between the front and rear faces. As we have seen, this difference creates a large drag like that seen below the transition Reynolds number"(http://www.aerospaceweb.org/question/aerodynamics/q0215.shtml).
Would the reduction in heat absorbed be significant enough to warrant a larger payload via lessening the weight of the heat shield?

This looks like a good question for Space.SE

It has already, by the same OP. @DecKonroyd, please do not double post.

You're trying to apply physics of laminar subsonic airflow to plasma encountered on reentry at Mach 50. From Design of an integral thermal protection system for future space vehicles: "It is required [...] the TPS be below certain limit in order to maintain the smooth aerodynamic profile of the vehicle. Excessive local deflection, such as a top surface dimpling, can lead to severe local aerodynamic heating, which may lead to catastrophic failures.

Duplicate of https://space.stackexchange.com/questions/23490/would-a-dimpled-heat-shield-reduce-heat-transfer-during-reentry

Golfballs are dimpled because the resulting turbulent boundary layer can follow the contour of the ball much better. Subsonic turbulent boundary layers have more drag than laminar ones, but fast separating boundary layers create high pressure drag, which more than compensates for the higher boundary layer drag.
So that is all great for subsonic golfballs. The re-entry vehicle though:

is air-braking upon re-entry and actually requires drag to slow it down;
enters hypersonically, with associated shock waves that have no intention of folding back or re-attaching over the back end of the sphere.

If the re-entry vehicle is a Space Shuttle with flat wings, at the end of the flight it does fly sub-sonic but even at this last bit is using speed brakes and deploys the landing gear as early as possible to slow down. For a re-entry sphere there seems to be no use for dimples: we want drag.

The point of re-entry vehicle it that it needs the drag, because it needs to slow down. So it is not optimized for lower drag, it is just optimized to minimize the transfer of heat from the compressed air to the body. Also keep in mind that vortex generators (dimples) work at subsonic speeds, but re-entry happens at hypersonic speeds.

@JanHudec Duh! Thanx for that, have re-written and will go quietly sit in a corner now.

Near as I know, the key to designing good re-entry vehicles or shielding is large flat plates, primarily because the design ensures the energy transfer from kinetic and potential energy of the craft to thermal energy  occurs mostly in heating the air flowing around the shape rather than the craft itself.  It sounds kind of counter intuitive, but doing this ensures the spacecraft remains as cool as possible and the least risk to structural damage from heating exists.  Therefore reducing drag is these applications is not a top priority.

Reducing drag is not just not a top priority. It is straight undesired. The thing is aerobraking—it needs high drag to slow down from the 7.9 km/s orbital speed down to safe landing.


text:
Why isn't an LPV SBAS approach considered a precision approach according to ICAO?

According to ICAO's classification, LPV SBAS approach is in the APV group, because it doesn't meet some specifications for precision approaches. But what exactly does it not meet?

Glossary:

LPV: Localizer performance with vertical guidance
SBAS: Space-based augmentation system
APV: Approach with vertical guidance

I am slightly surprised about LPV SBAS not being classified as a Precision Approach in ICAO, but the topic is relatively new to me. Do you have any references?

not a duplicate: that one asks IF this one asks WHY

Agreed. Not a duplicate.

Precision Approaches (PA), as you mention, have specific performance requirements, one of which is how "good" the vertical position measurement must be during an approach. In the case of a PA, ground systems either directly measure the aircraft's vertical position on the glide path (Precision Approach Radar in the case of parallel approaches), or provide a means to follow a precise vertical glide slope via a gauge in the cockpit.
For Approaches with Vertical Guidance (APV), there is vertical guidance, but the aircraft's vertical position is measured onboard the aircraft by either a GPS position source or a barometric sensor. Either of those sensors are subject to measurement errors:

Barometric Measurement Errors: ICAO Annex 10 section 4.4.2.4 defines the error model that is used for barometric altitude reporting systems. The 95% bound of the worst case is +/-282ft.
Barometric Setting Errors: Additional errors are introduced depending on what barometric MSL pressure is selected on the altimeter and how that compares to current (actual) atmospheric pressures.
GPS Measurement Errors: While GPS position sensors provide very good horizontal position, GPS vertical position is generally poor. According to the FAA, the 95% vertical error of GPS systems used in civilian contexts is on the order of 300ft and according to this Advisory Circular (section 5-7), geometric/GPS altitude does not meet requirements for use in air traffic control internationally.

Combining these errors with flight technical errors while flying the approach, the total error you can expect can add up quickly. Compare that to the fact that in the vertical guidance of an ILS improves the closer you get to the ground, you can quickly see why the alternatives of GPS or altimetry don't quite cut it...
So specifically to your question: For an approach to be a precision approach, you need precise vertical position measurements, which an SBAS cannot provide.

I'm a bit confused by this answer. If the vertical error is up to 300ft then LPV approaches couldn't exist. The LPV DA at my local airport is 285ft AGL, there's no way that's possible with 300ft of error. In fact, the FAA page you linked to quotes a position error of "less than 10 meters"; perhaps you meant 30ft, not 300ft? It also says "augmented by WAAS and GBAS, GPS will be able to supply a precision approach capability (CAT-I with WAAS [...])" And your final sentence says that SBAS can't provide precise vertical position, but that's exactly what an LPV approach does provide.

@Pondlife - You are correct. What I was referring to was the general FAA (as well as other regulators) skepticism of state measurement exclusively onboard aircraft.
Many of the model assumptions are outdated and artificially inflate worst case modeling, which contributes to slow adoption of new capability in aviation. Observed performance, in position accuracy is much better than what worst-case modeled performance could be. Therefore, system integrity (maximum undetected error) becomes the driving parameter. But, the reclassification in ymb1 answer is evidence that it might be changing

@Pondlife Non-SBAS GPS has a vertical error of 300ft; with SBAS, it drops to something like 30ft. But LPV still doesn’t qualify as Precision due to the “onboard” technicality.

It is a precision approach now, as mentioned already before, if Category I. The reference is: ICAO Annex X, Volume I, Chapter I, Definitions, Note 3, Remark (3)

This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review

There is a substantial distance between actual GPS/SBAS performance AND theoretical error modelling done to bound SBAS performance.
In the real world, HPL/VPL (horizontal/vertical protection levels) are in the 15 meter levels while measured errors are in the 2-3 meters level, rarely getting to 10 meters.
Actual errors are always 5-10 meters better than HPL/LPV levels.
The whole thing was modelled using theoretical worst case calculations that might never ever happen in the real world.
Essentially the FAA/EASA is just being way over zealous in what performance they allow LPV to be used for. LPV200 is only allowed to be used up to minimums, even in visual conditions, while ILS is allowed to be used for autoland below minimums if visual conditions are present.
Eventually FAA/EASA should allow for coupled LPV autopilot at least until 100 radar altitude.
Plus for now we're only using single frequency, GPS network only SBAS receivers. The next generation of SBAS will feature GPS+Galileo+Glonass+Compass+regional augmentation with dual frequency processing at the end user (aereal) receivers.
This will yield:
1 - Global LPV200 performance
2 - Currently we have a few minutes a day where LPV200 performance isn't available in the California coast and hours a day where LPV200 performance isn't available in northern Canada and Western Alaska. That should pretty much be gone. There could still be a few weak spots worldwide where LPV200 could be unavailable for a few minutes a day
3 - The ACTUAL performance of dual frequency/multi constellation SBAS should be good enough for CAT II approaches in the real world, but since mathematical models are used instead of real world performance, we might never get SBAS CAT II or it could take many decades.
The keys are:
With dual frequency service iono corrections are now calculated in real time at the end receiver.
With 4 constellations+regional we go from normal 9 GPS ranging sources to over 20 and sometimes 30 ranging sources. Actual typical accuracy should sub meter 99.99% of the time or CAT IIIc performance. But this is meaningless for aviation safety authorities, what matters to them is their ultra super duper pessimistic mathematical models that still predict errors that don't even allow for CAT II !
In conclusion, LPV200 is a precision approach. Even LPV250 is a precision approach too. That's in practice. But FAA/EASA don't like it.
There's also a conflict of interest in GBAS vs SBAS features. GBAS requires a per metro area installation and barely provides for full CAT I approaches today (including coupled landings) and eventually will provide CAT IIIa approaches. If SBAS could provide CAT IIIa, then GBAS is dead, and there are billions invested on that ! So people don't want SBAS features to invade their precious future GBAS performance envelope !

HPL/VPL are integrity indicators, not accuracy indicators so it does not make much sense to compare them to typical actual errors. Integrity is crucial for the safety case, because even though a 99.99% accuracy of 1 meter sounds great, you want to still to be safe if the system is in some degraded mode, and the accuracy cannot be met. That is what integrity monitoring is for and HPL/VPL is a metric for it in GNSS. FAA and EASA understand the difference between accuracy and integrity and prevent people who don't from making expensive mistakes.

authors: Андрей Кулаков


text:
Could a test crew replicate the 1961 DC-8 supersonic dive in a more modern airliner?
The first airliner to ever break the sound barrier was the DC-8, doing so in a semi-famous dive from 52,000' to 35,000' over the Edwards test range on August 21, 1961.
Could this supersonic dive be planned and reproduced by a suitable flight test crew in a more modern jet transport aircraft?

Why not?
There have been several cases of near-sonic and even supersonic dashes by the Boeing 747, and the damage to the China Airlines Flight 006 elevator was done by landing gear doors which ripped off when the main gear was extended and its doors hit the elevator.
There have been a few unintentional supersonic dives, and in those cases the actions taken by the crew to decelerate caused damage to the aircraft. TWA Flight 841, a Boeing 727 which rolled into a dive, and China Airlines Flight 006 overstressed the airframe, but both aircraft returned to service after repairs.
IAI experience tells me it needs a dive with a nose-down angle of 18° to get a Boeing 747 to Mach 0.98. Since almost all surfaces experience already supersonic flow at this speed, going the step to Mach 1.01 would need not much more, maybe 25°. Pulling up from such a dive by means of the stabilizer should entirely be possible without exceeding g limits.

Yeah -- I have read (unfortunately, just in a forum) that Boeing flight tested the 747 to Mach 0.99.  I suppose all it would take for an intentionally supersonic 747 dive to happen is one Boeing test crew going "Hey, Mach 1 isn't so far away after all..." and coming up with a test plan for taking the 747 there.

@Abdullah: Israel Aircraft Industries. I added a link to the text.

Gulfstream has also test dove their G500, G600, G650, and G700 airplanes past Mach 0.99 during test flights.  It is reasonable to conclude that all of these aircraft would be capable of very briefly breaking the sound barrier during flight in a dive, and still be within a recoverable capability.

Why not? Because the control surfaces become inoperable due to the load exceeding the specs.

Could an airliner exceed Mach 1 in a zero-G power dive and "safe"ly recover? reports that the famous DC-8 dive mentioned in the question needed to un-load the stabilizer (by pushing the nose down more!) so it could be moved to actually get out of the dive, because the load on the control surface prevented the motor from moving it.

@PeterCordes: OTOH, newer jetliners are optimized for transonic flight to a degree that older ones like the DC-8 weren't, so they're probably better-equipped to pull out of a supersonic dive without requiring unconventional aircraft handling.


text:
How often do V1 cuts come up in airline sim training?
Just how often do airline pilots practice V1 cuts when in the sim? Is it the kind of thing that turns up practically every sim session, or is it something that's much more sporadic?

During initial and upgrade training you will fly many V1 cuts. At every recurrent check ride you'll experience V1 cuts both as pilot flying and non flying pilot.
In our sim events the V1 cut would generally be a 600 RVR takeoff with 10 kt direct crosswind from the side that would fail. Not always though -- you expected the V1 cut on every takeoff.

That is to say, you can anticipate which side will fail once you know the wind direction in the sim? Seems to spoil the surprise lol

@kevin every takeoff has max crosswind and they don't always fail the worst case engine.

Sims are useful for three different groups of tasks that are difficult or a waste of time to do in the airplane:

Instrument approaches and departures
Normal Procedures
Emergency Procedures

V1 cuts come in the last category, and you will get plenty of them since you don't want to be doing them on the actual runway. You need to develop the proper intellectual acumen and muscle memory to react to the event so that you can handle one safely when it happens in real life.


text:
Are there any aircraft used in part 121 (aka scheduled airline) operations that do not require a type rating to fly?
Inspired by KeithS's question about ATPLs and category/class ratings, I figured I'd throw another type-rating/airline-operations puzzler at you: are there any aircraft currently in scheduled airline service (i.e. operated under part 121) which would not require a type rating to fly?  (I know part 135 operators often fly small aircraft due to the nature of their operation, with more intermittent or even on-demand service and the smaller locales they fly into.)

FYI: Part 121 is defined as operating "any turbojet powered airplanes, or airplanes having a passenger-seat configuration of more than 9 passenger seats, excluding each crewmember seat, or airplanes having a payload capacity of more than 7,500 lb." So you are looking for non-turbojet aircraft with payloads over 7,500 lb or more than 9 seats, and  MGTOW less than 12,500 lb. None have been posted so far.

@fooot -- Beech 99s and 100s and MU-2s fit into that box, at least when used in pax service.

Yes, they are in that window. I haven't found any in 121 service though.

@fooot -- that's interesting that the 99 is no longer in 121 service whatsoever; I'll do some more research on this.

Also -- FAR/CAR DHC-6 operations do not require a type rating, best I can tell (the Twotter's MTOW is exactly 12,500lbs); EASA takes a dim view of operating any turbine-powered aircraft w/o a type rating, though, apparently?

Cape air has a fleet of 83 Cessna 402s, some of which are involved in its Part 121 operation.

I suspect you're thinking about passengers, not freight, but Fedex is a part 121 operator that operates the Cessna 208 (Caravan), which does not require a type rating in the US.
Regional airlines in Hawaii and Alaska also operate the 208, but they seem to be part 135 operations.

Is Fedex actually operating those caravans on their certificate?  All of the caravans I can think of in Fedex paint are operated by smaller 135 carriers (e.g. Wiggins air).  The planes are dry-leased to the feeder carriers.

@casey Good question, I really have no idea how or if it's possible to check that.

Wikipedia says all of their prop aircraft are dry leased to contract carriers.

Cape Air seems to be a Part 121 carrier, and since they fly the Cessna 402, that might be an answer.